The present disclosure relates to a sheet conveyance device capable of conveying a sheet-like member, and an image forming apparatus having the sheet conveyance device.
In image forming apparatuses such as a printer, a copying machine, a facsimile machine, and a multifunction peripheral having these functions, a sheet conveyance device for conveying a print paper sheet (sheet-like member) is provided. In a conventional sheet conveyance device, a registration roller pair is provided for subjecting a print paper sheet to a registration operation (also called registration). Here, the registration operation means an operation of applying a conveyance force in the conveyance direction to the print paper sheet while the leading end of the print paper sheet is in abutment against a nip portion of the registration roller pair in a stop state. By this registration operation, inclination of the print paper sheet under conveyance is corrected. Also it becomes possible to align an image formation position in the print paper sheet with a transfer position of an image to be transferred to the print paper sheet.
Upon execution of the registration operation, the print paper sheet is deflected just before the registration roller pair. In a conventional sheet conveyance device, the registration roller pair is driven to rotate at such a timing that the defection is not excessively large, and the print paper sheet is conveyed downstream in the conveyance direction of the print paper sheet. However, a certain response time is required until the registration roller pair is actually driven after a drive signal for the registration roller pair is outputted. This response time is caused by various time loss such as transmission loss in a drive transmission mechanism (gear, clutch or the like) to the registration roller pair. Delay in drive of the registration roller pair due to the response time results in delay in conveyance of the print paper sheet, and as a result, deflection of the print paper sheet can excessively increase. In such a case, the deflected portion of the print paper sheet can collide with a guide surface of a sheet conveyance path to generate collision sound that is uncomfortable to the user. There is known a device that prevents generation of collision sound by reducing the conveyance speed of the print paper sheet in such a situation that collision sound is generated. However, in this device, the abutment of the print paper sheet to the registration roller pair is insufficient due to reduction in conveyance speed although generation of collision sound can be prevented. Therefore, inclination of the print paper sheet cannot always be corrected satisfactorily. Also, it is impossible to achieve speed-up of the image formation.
As a method for preventing generation of collision sound by deflection of a print paper sheet, there is known a method of measuring the response time in advance, and driving the registration roller pair by outputting a drive signal at the timing taking into account the response time. However, the response time varies from device to device, and can change owing to the deteriorated condition of the drive transmission mechanism, duration of use of the device and so on. Such variation or change in the response time will cause change in the amount of deflection of a print paper sheet during the registration operation, and the increased amount of deflection will cause generation of collision sound. In other words, even if the registration roller pair is driven at the timing taking into account the response time, it is impossible to securely prevent generation of collision sound in every sheet conveyance device under various environments.